Isopropyl alcohol is a common solvent in electronic cleaning, pharmaceutical and chemical industries. Its boiling point is about 82.6 ℃, its volatility is strong, and it is miscible with water in any ratio. These two properties determine its recovery route: condensation can be recovered, but condensate and water are mixed together, and separation is by rectification, instead of static water separation. The configuration of the two stages of condensation and rectification is straightened out, the recovery rate and reuse quality of isopropanol can be stabilized at a good level, and the disposal burden of waste liquid also becomes the reflux of raw materials. The value of recovery is not only in the saving of materials: the cost of outsourcing disposal of waste liquid is increasing year by year, and every ton of solvent recovered by oneself is subtracting the cost account.
The isopropanol tail gas of electronic cleaning and degreasing process has large air volume, low concentration and normal temperature emission; the tail gas of pharmaceutical and chemical processes has high concentration and fluctuates with batches. The nature of mutual solubility with water also brings a point: when the tail gas contains moisture, isopropanol will partially dissolve into water vapor, and the condensate contains both alcohol and water, and the water content varies with the working conditions. Before configuration, find out the concentration, air volume and moisture content of each tail gas: high-concentration stocks are condensed and collected directly, and low-concentration stocks are concentrated and processed. Only when the condensation temperature of wet stocks is properly deepened, the recovery rate can be guaranteed, and the load of subsequent rectification can be controlled.
The condensation temperature level of isopropanol is required to be medium, most of which can be recovered by two-stage water cooling, and the low temperature section further depresses the emission concentration; the management of frost layer in the low temperature section containing wet tail gas is arranged as usual, and defrosting is arranged according to the pressure difference trend. Condensate is a mixture of alcohol and water, and its concentration fluctuates with the inlet working conditions-the condensate with high concentration is directly distilled for purification, and the condensate with low concentration is uniformly treated with dilute liquid line. The condensed exhaust gas is discharged up to the standard through the control section. The system is air-tight managed to reduce the concentration dilution and cold waste caused by air leakage. The low point of the pipeline and the sealing requirements for condensate transportation are implemented together. The condensing load is calculated according to the maximum exhaust working condition. For the working condition with large fluctuation, the buffer volume is set to cut the peak. When the inlet condition is stable, the feed for the post-distillation is also stable.
| Segment | Features | Configuration considerations |
|---|---|---|
| boiling point | About 82.6 ℃ | Two-stage water cooling and low temperature section |
| water-soluble | Any ratio of mutual solubility with water | Distillation separation without water separation |
| azeotropic | Upper limit for ordinary distillation | Breaking azeotropic dehydration configuration |
| Condensate | Concentration fluctuates with working conditions | Dense-thin sub-line collection |
| Return supplies | Grade by Purpose | Batch-by-batch inspection and sub-use |
| Energy consumption | distillation energy concentration | thick and thin with steady feeding |
Alcohol-water separation is the core process of isopropanol recovery: ordinary distillation to the boiling point, the concentration can not be raised. The reuse quality is graded according to the purpose: electronic cleaning requires high purity and metal ions, and the refining depth is large; General cleaning and synthesis purposes, azeotropic concentration can be satisfied. Moisture and purity are tested batch by batch, and reused according to the test results. The ledger records the whereabouts of each batch, and the quality and cost are matched one by one.
Look at the refining depth and detection indicators: moisture, purity and metal ions can only be returned to high-end cleaning when they meet the standards one by one; General purpose azeotropic concentration products also have places to go. According to the detection classification reuse, quality and cost matching, do not blindly pursue uniform purity.
Dilute liquid concentration cost is high, according to the concentration of the file: medium concentration into the distillation concentration, dilute liquid priority set for concentration-insensitive processes.
The physical properties of the two are close, mixed recovery is feasible, but the product is mixed alcohol, the use is limited.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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